AFRICA Beyond “Slash and Burn”


Slash and burn. Most of us know this practice is bad news for the environment. Farmers clear land by cutting down all the vegetation (slashing) and then burn- ing away what’s left, releasing carbon dioxide into the air. After a few years, when the soil nutrients are depleted, farmers move on to a new plot of land and leave the old plot to fallow and even- tually replenish itself. In Sub-Saharan Africa, slashing and burning and poor soil quality feed into each other, creating an endless loop of land degradation and inefficiency. But what if there were a way to keep farmers from burning up all the biomass left behind by slashing while also enhancing the soil’s retention of nutrients and water?


BIOFUEL


Biochar—biomass burned without oxygen to form charcoal—has the potential to


end the slash-and-burn cycle. Studies have shown that biochar added to soil increases the soil’s ability to retain water and nutrients. But for people to use it, the technology needs to be both effective and affordable. Tat’s where IFPRI research fellow Alex De Pinto saw an opportunity.


“Te biophysical side of this has been explored,” De Pinto said. “Now we need to work out the economic side.”


De Pinto is launching a study of the economic viability of “slash and char” as an alternative to slash and burn, work- ing with partners at Ghana’s Soil Re- search Institute and Kwame Nkrumah University of Science and Technology, who are running trials on how biochar affects the soil. De Pinto’s research will focus on the costs: clearing the land,


other farms


transporting the biomass, turning that biomass into biochar, and distributing the biochar to farmers.


Depending on his results, De Pinto sees many possibilities for biochar to improve agriculture in developing countries. Us- ing biochar should lead to richer soil and increased productivity, reducing farmers’ need to clear new land. It could also be linked to cap-and-trade or carbon- payment schemes, giving farmers not only richer soils and increased yields but also a monetary incentive to capture and use carbon rather than releasing it into the air by simply burning a field.


Could biochar help spell the end of slash and burn? De Pinto is working on the answer.


– Adrienne Chu


Farms have a lot of leftovers: corn stalks, wood chips, animal manure, rice hulls, tree bark, grasses, and more. One way to put these leftovers, or biomass, to good use is to transform them. They can be burned without oxygen to form biochar, a type of charcoal that farmers can use for fuel or mix into the soil.


PYROLYSIS


Intense heat (sometimes more than 1,000˚ F) with no oxygen creates a fine-grained, highly porous charcoal (biochar).


Biomass is picked up from other farms and delivered to the kiln.


Biochar is bought and sold at market.


ATMOSPHERIC BENEFITS • Stores carbon


• Reduces methane and nitrogen dioxide soil emissions • Reduces odor (by not leaving biomass to rot)


SOIL BENEFITS


• Improves fertility • Decreases nutrient runoff • Improves water retention


BIOMASS


PYROLYSIS KILN


Biochar byproduct fuels this truck.


Farmers mix biochar into the soil.


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